Noise cancelling systems are known to provide good music reproduction environments for listeners (users) when they listen to music and the like through earphones, headphones, and the like by reducing (cancelling) noise of external environments. In the noise cancelling systems of the related art, a primary process of reducing noise is an analog process. However, noise cancelling systems based on digital processes have also recently been developed, and headphones equipped with the noise cancelling systems based on digital processes have been commercialized and are available in the marketplace. The noise cancelling systems based on the digital processes are equipped with a plurality of noise cancelling modes of the digital processes as well as high noise cancelling performance based on the digital processes. A listener can selectively use an optimal mode according to noise because the plurality of noise cancelling modes are provided (for example, Patent Literature 1).
Furthermore, some headphones equipped with the noise cancelling systems are provided with a function of analyzing a state of ambient noise when the user simply presses a button and automatically selecting an optimal noise cancelling mode (an optimal-mode selection function). If the optimal-mode selection function is executed in the headphones, the headphones first stop an operation of outputting music or the like, and also stop a noise cancelling function. The headphones collect a noise sound from a microphone provided on their inner or outer side, analyze the collected sound, and select an optimal mode based on an analysis result. If the optimal mode is selected, the headphones resume the noise cancelling function by switching to the selected mode, and resume the operation of outputting music or the like.